1. Field of the Invention
The present invention relates to reassigning storage volumes from a failed processing system to a surviving processing system.
2. Description of the Related Art
In certain computing environments, multiple host systems may communicate with one or more control units, such as an IBM Enterprise Storage Server (ESS)®, for data in a storage device managed by the ESS receiving the request. The control unit manages access to storage devices, such as interconnected hard disk drives through one or more logical paths. (IBM and ESS are registered trademarks of IBM). The interconnected drives may be configured as a Direct Access Storage Device (DASD), Redundant Array of Independent Disks (RAID), Just a Bunch of Disks (JBOD), etc.
Typically, the storage systems managed by the control unit includes numerous interconnected hard disk drives from which volumes are configured for the hosts to use. The storage devices may be configured as one or more arrays, such as RAID arrays, and the array storage space then assigned to volumes.
Certain control units include dual processing complexes or systems, each managing access to different sets of logical control units, where each logical control unit is assigned a plurality of storage volumes, such as logical volumes. If one processing complex fails, then the logical control units assigned to the failed processing complex would be reassigned to the surviving processing complex. As part of this failover, the surviving processor sends unit check status to each host for each storage device to which the host is connected to alert them of the failure so that the hosts may redrive any pending Input/Output (I/O) requests. As control units are allowing hosts to connect to ever increasing numbers of storage volumes, the hosts may have to consume substantial computational resources to handle unit checks received as part of a failover to the storage devices (volumes) to which the host is connected.